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 The findings, published in the American Journal of Tropical Medicine
and Hygiene, show that as with many related viruses, including
dengue and yellow fever, Zika can be transmitted from female
mosquitoes to their offspring.
Dr. Robert Tesh of the University of Texas Medical Branch in
Galveston, Texas, a study co-author, said the fact that the virus
can be passed along to mosquito offspring makes Zika harder to
control.
"Spraying affects adults, but it does not usually kill the immature
forms - the eggs and larvae. Spraying will reduce transmission, but
it may not eliminate the virus," he said.
Although Zika generally causes mild disease in adults, it is a major
threat to pregnant women because it has been shown to cause the
severe birth defect known as microcephaly and other brain
abnormalities.
The ongoing Zika outbreak was first detected last year in Brazil,
where it has been linked to more than 1,800 cases of microcephaly,
and has since spread rapidly through the Americas.
Aedes aegypti, the mosquitoes that carry Zika, lay eggs in small
containers of water. Homeowners have been advised to dump out
containers of water on their properties. When the water is dumped,
the eggs cling in a ring around the water line, where they remain
dormant until the next rain, when they can hatch.
Scientists studying Zika wanted to find out whether some of the
offspring from these tropical mosquitoes might carry the virus,
helping to perpetuate an outbreak during dry seasons.
To find out, researchers injected female Aedes aegypti mosquitoes
raised in a laboratory with Zika. They were then fed, and within a
week, they laid eggs. The team collected and cared for the eggs
until they hatched into adult mosquitoes, and counted the ones that
carried the Zika virus.
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They found the virus present in one out of every 290 mosquitoes
tested.
"The ratio may sound low," Tesh said, "but when you consider the
number of Aedes aegypti in a tropical urban community, it is likely
high enough to allow some virus to persist, even when infected adult
mosquitoes are killed."
Tesh said the next step is to show that mosquitoes are actually
passing Zika to their offspring in the wild.
Experts fighting Zika in the Wynwood neighborhood of Miami have
announced aerial spraying campaigns using pesticides that kill both
adult mosquitoes and mosquito larvae.
For homeowners in affected areas, Tesh advised people to dump
standing water from containers on their property and scrub them
thoroughly to remove eggs and larvae. They should also remove any
objects from their yards that could collect water.
(Reporting by Julie Steenhuysen; Editing by Bernard Orr)
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